grid: now has a new OnHeaderClick event
grid demo: fixes index out of bounds error when deleting rows.

We never checked to see if there are any rows to delete.
grid demo: adds OnHeaderClick event handler test

- also updated project file settings for Lazarus IDE usage.
edittest: BeginDraw/EndDraw calls were not needed.
edittest: trackbars were never disabled
edittest: define the height of ComboBox widgets to match height of Edit widgets
MessageDialog: BeginDraw/EndDraw is not needed in HandlePaint()
agg: fixes bug when attaching a Image to TAgg2d doesn't draw lines.

I forgot to setup the internal dash generator in the TAgg2d constructor.
The AggCanvas did this automatically in the Canvas.BeginDraw() call, but
using TAdd2D via the .Attach(bitmap) didn't.
agg: removed the pointless casts. The x & y params are already PDouble's
agg: Add agg_renderer_base.fill(color) method for blending a color.

This complements the clear(color) method, which copies the color.
This is a port of r82 from AGG project on SourceForge.
agg: surfaced the new Fill(color) method in TAdd2D and agg_2d
Merge branch 'develop' into lesswindows